1. Field of the Invention
This invention relates to mixed basic metal oxide/sulfide catalysts useful for production of higher hydrocarbons by oxidative coupling of methane, production of higher hydrocarbons by oxidative coupling of aliphatic and alicyclic hydrocarbon compounds with aliphatic and alicyclic substituted aromatic hydrocarbon compounds to form a longer substituent hydrocarbon on the aromatic ring, and production of unsaturated aliphatic and alicyclic chains by dehydrogenation of aliphatic and alicyclic hydrocarbon compounds and aliphatic and alicyclic substituted aromatic hydrocarbon compounds. Reaction of methane with oxygen in the presence of a mixed basic metal oxide/sulfide catalyst in accordance with this invention results in high conversion of methane with selectivity for ethane and ethylene products. Reaction of methane with toluene and oxygen in the presence of a mixed basic metal oxide/sulfide catalyst according to this invention results in high conversion to form styrene. One important dehydrogenation is the reaction of ethylbenzene in the presence of a mixed basic metal oxide/sulfide catalyst according to this invention to produce styrene.
2. Description of the Prior Art
Methane is currently available in large quantities from natural gas, anaerobic digestion of organic material, and chemical processing sources. However, use of methane as a chemical feedstock has been limited due to its high stability. It has been highly desirable to develop a catalyst for such reactions to enable operation under milder conditions with greater control over thermodynamic and kinetic processes as well as provide product selectivity and high reaction rate.
Oxidative coupling of methane to form higher hydrocarbons has been shown to be effected over a number of metal oxides, but yields of desired products have been low, as discussed by Keller, G. E. and M. M. Bhasin, J. of Catalysis 73, 9-19 (1982). Sodium and lead on alumina has been found to catalyze the formation of ethane and ethylene from methane, as disclosed in Hinsen, W. and M. Baerns, Chem.-Ztg., 107, 223-226 (1983) and Hinsen, W., W. Bytyn and M. Baerns, Proc. 8th Int. Congr. Catal., Berlin, III 581-592 (1984). Several U.S. patents teach a series of supported metal oxides which while effective for the conversion of methane to ethane and ethylene, are based on reducible metal oxides and used in a stoichiometric fashion by alternately exposing them to an oxidizing atmosphere and then to methane in the absence of oxygen. U.S. Pat. Nos. 4,443,644; 4,443,645; 4,443,646; 4,443,647; 4,443,648; 4,443,649; 4,444,984, 4,499,322; 4,499,323; 4,499,324; and 4,523,049.
Later work has demonstrated that magnesium oxide and calcium oxide, when promoted with alkali metal salts, are active for oxidative coupling of methane to ethane and ethylene in the presence of oxygen. See Kimble, James B. and John H. Kolts, "Oxidative Coupling of Methane to Higher Hydrocarbons", Energy Progress, Vol. 6, p. 227 (1986); Driscoll, D. J., W. M. Martir, J. Wang and J. H. Lunsford, J. Am. Chem. Soc. 107, 58-63 (1985); and Ito, T., J. Wang, C. Lin and J. H. Lunsford, J. Am. Chem. Soc. 107, 5062-64 (1985). These later Catalysts have the advantage of operating continuously, not requiring regeneration or pretreatment.
Borates and boron compounds have been used in partial oxidation of hydrocarbons, such as boric acid to oxidize long chain normal paraffins in the liquid phase (Illingworth, G. F. and G. W. Lester, ACS Petroleum Division Preprints, 12, No. 3, 161 (1967)) and oxidation of n-dodecane in the liquid phase to the corresponding alcohol (Lee, K. W., M. J. Choi, S. B. Kim and C. S. Choi, Ind. Eng. Chem. Res. 26, 1951 (1987)). Boric acid has been used by coating reactor walls in the combustion of methane to eliminate free radical destruction at temperatures of less than 513.degree. C. (Kegeyan, E. M., I. S. Vardanyan and A. B. Nalbandyan, Kinetics and Catalysis 17, No. 4,749-754 and No. 4,755-759 (1976))
A number of publications describe oxidative methylation of toluene performed in Russia: Chemical Abstracts 97:127153K (I982) teaches non-catalytic methylation of toluene depended mostly on pressure and PhMe/O/CH.sub.4 molar ratio; Chemical Abstracts 99:70137t (1983) teaches oxidative methylation of toluene using a Ni-V oxide or V oxide catalyst; Chemical Abstracts 101:74734t (1984) teaches oxidative methylation of toluene in presence of oxygen (max. 15 percent in reaction mixture) results in products including styrene; Chemical Abstracts 101:38205 n (1984) teaches simultaneous production of styrene, ethylbenzene, benzene, and phenols by reaction of toluene with C.sub.1-4 alkanes in the presence of oxygen and Fe.sub.2 O.sub.3 or TiO.sub.2 at 600-800.degree.. Productivity increased at higher pressure in presence of H.sub.2 O.sub.2 and/or (Me.sub.3 C).sub.2 O.sub.2 ; and U.S. Pat. No. 3,830,853 teaches reaction of toluene with a lower paraffin hydrocarbon in the presence of oxygen at 600.degree.-900.degree. C. and space velocity of 2000-10000 hour.sup.-1.
Styrene is an important commercial unsaturated aromatic monomer used extensively in the manufacture of plastics by polymerization and copolymerization. On a commercial scale, the great majority of the world's styrene is produced by dehydrogenation of ethylbenzene. A review of styrene synthesis processes is given in Kirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, Vol. 21, Styrene, pgs. 770-801. One commercial process for production of styrene is the UOP Styro-Plus process using ethylbenzene and superheated steam under vacuum for the catalytic dehydrogenation of ethylbenzene as taught by Ward, D. J. et al, Hydrocarbon Processing, Vol. 66, No. 3, March 1987, pgs 47-48. Use of cokecovered alumina and boron/alumina catalysts for oxidative dehydrogenation of ethylbenzene is taught by Fiedorow, R., W. Przystajko, M. Sopa and I. G. Dalla Lana, The Nature and Catalytic Influence of Coke on Alumina: Oxidative Dehydrogenation of Ethylbenzene, Journal of Catalysis 68, pgs. 33-41 (1981). Oxidative dehydrogenation of ethylbenzene to styrene over metal pyrophosphates, such as cerium, tin, zirconium, and titanium phosphates and calcium magnesium, strontium, barium, nickel, aluminum, thorium, zinc and silicon phosphates is taught by Vrieland, G. E., Oxydehydration of Ethylbenzene to Styrene over Metal Phosphates, Journal of Catalysis 111, pgs. 1-13 (1988). This article teaches the condensed phosphate surface is the dominant factor as a catalyst and that the cation has little or no effect.